Permanent Deformation of Steel Pipe Piles Penetrating Compacted Fill at Wharf on Port Island

Abstract

ABSTRACT A pile inclinometer survey is conducted for the steel pipe piles supporting a four-story steel structure that survived the Hyogoken-Nambu earthquake, together with some other measurements, in order to clarify the degree of integrity of the building foundation. The building is located on a wharf surrounded by the sea on three sides. At the site, fill deposits about 20 m thick have been compacted by the vibro-rod compaction method. Subsurface investigations are also conducted for the compacted fill and underlying soil deposits. The investigations reveal the following: (1) ground subsidence due to the earthquake is estimated to be 30 to 100 mm; (2) the compacted fill has 60 to 80 percent greater resistance to liquefaction than untreated fill; (3) piles about 40 m long have been deformed not only above the interface between the reclaimed fill and the underlying alluvial clay layer (Mal3 layer), but also at the lower interface of the Mal3 layer; (4) the pile heads are judged to have been moved by at most 344 mm in the north-northeast to northeast direction. The moved distance and direction of the pile heads are explained on the basis of the compiled data regarding the relationships among the moved distance of pile-supported buildings, the distance between the buildings and quay walls, the lateral displacement of the quay wall crests and the thickness of the reclaimed fill.